During the drilling and completion of oil and gas wells, it may be necessary to engage in ancillary operations, such as evaluating the production capabilities of formations intersected by the well bore. For example, after a well or well interval has been drilled, zones of interest are often measured or tested to determine various formation and fluid properties. These tests are performed in order to determine whether commercial exploitation of the intersected formations is viable and how to optimize production. The acquisition of accurate data from the well bore is critical to the optimization of hydrocarbon wells. This well bore data can be used to determine the location and quality of hydrocarbon reserves, whether the reserves can be produced through the well bore, and for well control during drilling operations.
The collected data is contained in a survey or “log,” then analyzed to determine one or more properties of the formation, sometimes as a function of depth. Many types of formation evaluation logs, e.g., mechanical, resistivity, acoustic and nuclear, are recorded by appropriate downhole instruments supported by a housing. The housing may include a sonde with the instruments and a cartridge with associated electronics to operate the instruments in the sonde. Such a logging tool is lowered into the well bore to measure properties of the formation. To reduce logging time, a combination of logging tools may be lowered in a single logging run.
Often, logging tools are lowered into vertical well bores by wireline. Gravity moves the logging tools into the well bore, and the wireline is used for electrical communication and support for pulling the logging tools out of the well bore. Logging deep, extended, deviated or horizontal wells can be problematic with wireline. The wireline provides no driving force for pushing, rather than pulling, logging tools further into the well bore. To log such well bores, tubulars such as coiled tubing or drill pipe transport logging tools into the well bore. Pipe, tubing, tubular and like terms may all be used to reference such a conveyance. In some cases, wireline logging tools are adapted for drill pipe deployment. The logging tools are coupled to the operational end of the tubular and may be extendable from the tubular.
Pipe conveyed well logging tools are relatively fragile as compared to the drill string from which they are deployed. Further, extendable well logging tools are exposed to the downhole environment. When a borehole is drilled, it is seldom smooth and regular. It has cave-ins, erosions, washouts, shales and clays that squeeze into the hole, ledges, protrusions and other rugosity. The drill string can impart large forces to the logging tools, easily capable of damaging any deployed arms or even the main body of the logging tools themselves. Since some tools can be damaged with compression forces on the order of 10,000 lbs., the tools are very susceptible to much greater forces produced by a drill string. When the tools are extended and latched into the bottom of the drill string, the downward motion of the pipe can be transmitted directly to the logging tools. If the bottom of the logging tools are forced into a washout or against a ledge, a substantial force can be transmitted to the tools by the drill string. Upward forces on the logging tools, as well as obtrusive debris in the well bore, can also cause unwanted adjustments of the expected distance between the extended logging tool and the drill pipe, thereby affecting the accuracy of the depth-dependent measurements and formation properties derived therefrom. In some cases, pipe conveyed logging tools do not have communication to the surface and cannot be directly controlled (e.g., powered up, motored open and closed, etc.) from the surface as is customary for purely wireline tools.
These and other limitations of the prior art are overcome by the embodiments, arrangements and processes as taught herein.